You can flag a message that you write to have a return receipt message sent back to you when the recipient opens your message. When you compose a message you select Return Read Receipt from the Options menu on the Compose toolbar. The recipient can choose to return the read receipt or not.
In Preferences>Mail's Read Receipt section, users can set their preferences for messages that are flagged with a return receipt request. The following options can be set:
Never send a read receipt. This is the default. When a message is received with a return read receipt request, the request is ignored. The recipient is not aware of the request.
Always send a read receipt message. A return read receipt message is automatically sent when the message flagged for return read receipt is opened.
Ask me. Recipients are asked if they want to send the return receipt.
A return read receipt message is not sent if a recipient selects more than one message and right-clicks and selects Mark As Read.
Note: The return read receipt flag does not work for messages that are sent to users on systems other than ZWC